This application relates to and claims priority to corresponding Japanese Patent Application No. 288705/1999 filed Oct. 8,1999 and which is incorporated by reference herein.
(1) Field of the Invention
The present invention relates to a sifter in which a plurality of sifter frames provided with sifting nets which are stacked one on top of the other within one and the same machine frame in the sequence of sizes of meshes, the machine frame being rotatingly oscillated with respect to the horizontal plane by a vertical rotary oscillating axis thereby sifting powdery particles on the basis of particle diameters, and more particularly to an apparatus for exchanging sifter frames in which, during the maintenance (exchange of the sifter frames) of the sifter, the sifter frames can be easily taken out of the machine frame.
(2) Description of the Related Art
A prior art sifter as shown in FIG. 1 is known, in which a plurality of sifter frames provided with sifting nets are stacked one on top of the other within one and the same machine frame in the sequence of sizes of meshes, the machine frame being rotatingly oscillated with respect to the horizontal plane by a vertical rotary oscillating shaft thereby sifting powdery particles on the basis of article diameters.
FIG. 1 shows an outside appearance of the prior art sifter in which a plurality of sifter frames 101 are stacked on a sifting machine frame 102, and are fixed unitarily to the sifting machine frame 102 by bolts 103 and nuts 104. The sifting nets of the sifter frames 101 are stacked one on top of the other in such a way that lower the nets are positioned the meshes of the nets gradually become finer, and that material particle objects are introduced from the topmost sifting net and finer particles can be taken out from lower sifting nets. The sifting machine frame 102 has at its central portion a vertical rotary shaft 105 for effecting rotary oscillation and, with the rotation of the rotary shaft 105, the sifting machine frame 102 is caused to oscillate in a horizontal direction. When the sifting machine frame is oscillated, the sifter frames 101 in the machine frame are also oscillated. The particle objects introduced from the inlet 106 onto the uppermost sifter frame are sifted due to the rotary oscillation of the sifting nets and different meshes of the sifting nets, and the sifted particles are discharged from the outlet 107 below. The sifter frames are supported at their four corners by glass fiber rods 108 so as to allow the oscillation of the sifter frames.
The conventional sifter is configured as above so that, for exchanging the sifter frames 101, first the bolts 103 and the nuts 104 of the sifter frames 101 which are unitarily stacked on the sifting machine frame 102 are loosened, and the sifter frames, one at a time, are taken out from the sifting machine frame 102. Thereafter, the inspection is made for any holes in the nets, the tense conditions of the nets, any leakage of particle objects, etc. and, if any problems are found, the sifter frames 101 are replaced by new ones. When exchanging for the new sifter frames 101, the reverse work is performed, that is, the sifter frames 101 are stacked in the sifting machine frame 102 one by one and, on reaching a predetermined number, they are unitarily fastened by the bolts 103 and nuts 104.
The exchanging operation as above involves heavier work as the number of the sifter frames increases. For example, in the case where there are six sifting chambers and, in each chamber, there are 20 to 30 stages of the stacks of the sifter frames 101, the time required for exchanging the sifter frames is about 80 minutes for each chamber, which means that the total time of eight hours is required for six sifting chambers and shows that such a great time is necessitated in the conventional exchanging operation.
Further, the sifter frames stacked in 20 to 30 stages reach the height of two to three meters from the ground which required working on a stepladder in a precarious condition, and there was a risk of collapsing of the stacked sifter frames. Also, the total weight of the sifter frames stacked in 20 to 30 stages amounted to 200 Kg so that the exchanging work itself involved risk.
In view of the above problems, an object of the present invention is to provide means for exchanging sifter frames which enables the reduction in the hard work involved in exchanging the sifter frames and in the exposure of the workers to the risk and which enables easy exchange of the sifter frames.
In order to solve the problem, according to one aspect of the invention, there is provided a method for exchanging sifter frames of a plan sifter, in which a plurality of sifter frames having nets of different meshes are stacked one on top of the other, the stacked sifter frames are accommodated and fixed in a sifting chamber provided within a machine frame, and the machine frame is suspended from above and caused to be oscillated for sifting powdery particles, the method comprising the steps of:
stacking the plurality of sifter frames in advance outside the machine frame and holding the sifter frames in a unitary form;
placing the unitary formed sifter frames in the sifting chamber when accommodating the sifter frames in the sifting chamber;
fixing the unitary formed sifter frames accommodated in the sifting chamber; releasing the fixing of the sifter frames when drawing out the sifter frames from the sifting chamber; and
drawing out the sifter frames to outside the machine frame in the state in which the sifter frames are stacked in the unitary form.
With the above configuration, when the sifter frames are taken out from a plurality of sifting chambers provided within the machine frame, it is not necessary to take out the sifter frames one at a time from each sifting chamber to inspect the existence of any holes in the nets, any problem in the tense condition of the nets, any leakage of particle objects, etc. and then to exchange the sifter frames and, when the sifter frames are accommodated into each of the sifting chambers, the sifter frames are stacked in advance outside the machine frame and the unitary formed sifter frames are accommodated in each sifting chamber so that, even when the number of the sifter frames is large, the exchanging operation can be easily carried out. Also, the number of the stacked sifter frames can, in that state, be taken out of the machine frame. Then, the accommodated unitary formed sifter frames are fixed in each sifting chamber for sifting operation and, when the sifter frames are taken out from each sifting chamber, the fixed state of the sifter frames is released and the stacked unitary formed sifter frames are taken out of the machine frame. For example, in the case of the plan sifter where there are 20 to 30 stages of the sifter frames in each sifting chamber and there are 6 sifting chambers, the time conventionally required for exchanging operation was about 80 minutes for each chamber but this has been reduced to about 40 minutes, half the time, and in the case of the plan sifter having 6 chambers, only about 4 hours are required, half the time which was conventionally required.
According to another aspect of the invention, there is also provided an apparatus for exchanging sifter frames of a plan sifter in which a plurality of sifter frames having nets of different meshes are stacked one on top of the other, the stacked sifter frames are accommodated and fixed in a sifting chamber provided in a machine frame, and the machine frame being suspended from above and caused to be oscillated or shaken for sifting powdery particles, the apparatus comprising:
means to stack the plurality of sifter frames and hold the unitary formed sifter frames;
means to transport the unitary formed sifter frames to the sifting chamber for accommodating the sifter frames in the sifting chamber, and from the sifting chamber for drawing out the sifter frames; and
means to fix the sifter frames by giving appropriate pressure vertically downwardly from above to the sifter frames accommodated in the sifting chamber.
With the sifter frame holding means, the stacked sifter frames can be unitarily held and, with the sifter frame transporting means, the sifter frames can be transported out easily to outside the machine frame. When the sifter frames are fixed within the sifting chamber, the stacked sifter frames have conventionally been fixed by bolts and nuts. However, according to the invention, the stacked sifter frames are automatically fixed or released by the sifter frame fixing means thereby enabling to reduce the heavy labor involved in the operation.
The apparatus for exchanging sifter frames of a plan sifter is one in which the means to transport the sifter frames includes a first moving cart for moving the unitary formed sifter frames from a location at which the sifter frames are in contact with the machine frame to a predetermined location different from a location of the machine frame, and a second moving cart for moving, when the first cart is at the location at which the sifter frames are in contact with the machine frame, the unitary formed sifter frames between aboard the first moving cart and inside the sifting chamber; whereby, when the sifter frames are accommodated in the sifting chamber, the first moving cart is moved to the predetermined location different from the location of the machine frame, the unitary formed sifter frames are placed via the second moving cart on the first moving cart, further the first moving cart is moved to the location at which the sifter frames are in contact with the machine frame and, after the second moving cart is moved from aboard the first moving cart to inside the sifting chamber, the second moving cart is drawn out and the sifter frames are accommodated; and when the sifter frames are drawn out from the sifting chamber, the first moving cart is moved to the location at which the sifter frames are in contact with the machine frame, the second moving cart is inserted into a bottom portion of the unitary formed sifter frames, and the second moving cart is moved from aboard the first moving cart from inside the sifting chamber and the sifter frames are drawn out. With the sifter according to this configuration, even when the sifter frames are stacked, for example, in 20 to 30 stages weighing about 200 kg, the exchanging operation is safe because of the employment of the first and the second moving carts, and moreover the exchanging operation is easy and fast.
The apparatus for exchanging sifter frames of a plan sifter is one in which the means to transport the sifter frames includes a first moving cart for moving the unitary formed sifter frames from a location at which the sifter frames are in contact with the machine frame to a predetermined location different from a location of the machine frame, and a second moving cart for moving, when the first moving cart is at the location at which the sifter frames are in contact with the machine frame, the unitary formed sifter frames between aboard the first moving cart and inside the sifting chamber; and the sifter frame fixing means includes a sifter frame fixing device provided above the sifting chamber and giving appropriate pressure vertically downwardly from above to the sifter frames accommodated in the sifting chamber, and an elevating means provided below the sifter frame fixing device and allowing the upward-and-downward movements of the unitary formed sifter frames accommodated in the sifting chamber. According to the plan sifter having this configuration, with the first moving cart, a plurality of sifter frames can be stacked in advance outside the machine frame to stand by and, with the second moving cart, the unitary formed sifter frames may be pushed into the sifting chamber so that, with a simple operation, the sifter frames can be exchanged. Also, the sifter frame fixing means facilitates the unitary formed sifter frames to be easily fixed or released. Further, when the second moving cart is drawn out from the unitary formed sifter frames at the sifting chamber, the sifter frame elevating means may be operated so that, while the unitary formed sifter frames are elevated, the second moving cart may easily be drawn out.
The apparatus for exchanging sifter frames of a plan sifter is one in which the second moving cart is configured by a cart portion in a low floor form on which the unitary formed sifter frames are placed, and by wheels provided under a bottom surface of the cart portion. The sifter frame elevating means is configured by an air cylinder for elevating the unitary formed sifter frames separately from the cart portion.
The apparatus for exchanging sifter frames of a plan sifter is one in which the second moving cart is configured by a bottom box on which the unitary formed sifter frames are placed, and by wheels provided inside the bottom box and allowed to come in and out of the bottom box; and the elevating means are configured by wheels allowed to come in and out of the bottom box.
The apparatus for exchanging sifter frames of a plan sifter is one in which the first moving cart includes a leg portion having horizontally adjusting legs and casters, a base portion supported by the leg portion, a jack portion capable of appropriately jacking up the base portion with a fulcrum point as the center, a lift base for raising the jack portion to an appropriate height, and a placement base provided on the lift base with a horizontally adjusting portion interposed therebetween. The first moving cart is enabled to move by the casters and, during the operation, the horizontally adjusting legs may be in a fixed position so as to make the moving cart stable. Further, the placement base can be adjusted by the jack portion so that the height thereof can be substantially the same as that of the bottom portion of the sifting chamber of the sifter.
Further, the apparatus for exchanging sifter frames of a plan sifter is one in which the apparatus is provided with a first lock means to fix the first moving cart and the sifting chamber, and a second lock means to fix the first moving cart and the second moving cart, the first lock means and the second lock means being used when the unitary formed sifter frames are accommodated in and taken out of the sifting chamber. When the unitary formed sifter frames are exchanged, the first and the second moving carts are prevented from moving so that even when the sifter frames are stacked, for example, in 20 to 30 stages weighing about 200 kg, the exchanging operation is safe because of the employment of the first and the second moving cart, and moreover the exchanging operation can be carried out in a safe manner.